I’ve only briefly scanned the post so really cannot critique or praise (though get the sense the latter would be more likely). I did want to mention an article you might like related to the general problem here. I’ve forgotten the actual title but it was in the 1993 or 1994 Journal of Political Economy. Daniel Sutter. The tile has something about the Merchant Guilds.
The general thrust of the argument (as I recall) was that rather than being the usual monopoly, rent-seeking institution we typically here they were (at least the one examined) they were really institutions that were solving a problem of thin markets and establishing rule to promote competition (fair markets?).